1. Field of the Invention
This invention relates to a device for detecting the position of an elevator car.
2. Description of the Prior Art
In an elevator control system, it is essential to detect the position of the elevator car, and for this purpose floor selectors are normally utilized.
There are a variety of types of floor selectors, but only recently computer and microprocessor devices have been adapted to perform the necessary computations formerly effected by means of mechanical selectors.
One known method is carried out by the provision of outwardly projecting switch actuating cams disposed at predetermined positions between adjacent floors within a hoistway or elevator shaft. An interfloor detector is installed on the elevator car and is adapted to operate when it engages one of the cams. A floor level detector is likewise installed on the elevator car and is similarly adapted to operate when it engages one of the cams. A position-detecting circuit computes and stores a car position signal from the information received from the interfloor and floor level detectors each time the detectors operate in response to the movement of the elevator car.
However, should the contacts of the detectors shake for any reason, or should the elevator car be moved slightly in the vicinity of the cams by manual control, the aforementioned computation is repeated each time contact is made by the detectors, and as a result the calculated position of the elevator car will be different from the actual car position.